A half-bridge includes two electronic switches, a first electronic switch, which is also referred to as high-side switch, and a second electronic switch, which is also referred to as low-side switch. The switches have their load paths connected in series, where in operation of the half-bridge the series circuit with the two switches is connected between terminals for a first supply potential and a second supply potential. An output of the half-bridge may be formed by a circuit node that is common to the load paths of the two switches.
Half-bridges can be employed in a wide range of different applications, such as motor drive circuits, switched-mode power supplies, or full-bridges (H-bridges) including two half-bridges. The electronic switches employed in a half-bridge are, for example, MOS transistors, such as MOSFETs (metal oxide semiconductor field effect transistors) or IGBTs (insulated gate bipolar transistors).
MOS transistors are voltage controlled device that can be switched on and off by applying a suitable gate drive voltage between a gate terminal acting as a control terminal and a source terminal (in a MOSFET) or an emitter terminal (in an IGBT). A plurality of different types of MOS transistors are available that have different voltage blocking capabilities, from several 10V up to several kV (kilovolts), different on-resistances, and/or different threshold voltages. The “threshold voltage” is the gate drive voltage at which the MOS transistor starts to conduct. Usually, MOS transistors with a low voltage blocking capability have a low threshold voltage, while MOS transistors with a high voltage blocking capability have a high threshold voltage. The absolute value of the gate drive voltage to be applied in order to completely switch an MOS transistor on, so that the on-resistance has a minimum, is higher than the threshold voltage. There are MOS transistors that can be switched on an off using logic level drive signals with a maximum signal level of 5V or 3.3V, while other MOS transistors require gate drive voltages with higher maximum voltage levels.
In order to prevent a current shoot-through when the half-bridge is in operation, the two switches should be driven such that they are not switched on (in an on-state) at the same time. Further, there should be a dead time between a time of switching off one of the two switches and a time of switching on the other one of the two switches.
There is a need to provide a drive circuit, in particular a drive circuit for driving a half-bridge, that is configured to generate a first and a second drive signal with adjustable drive signal ranges and with an adjustable dead time.